xv MOUNT VUNGALEI 213 



the felspar and pyroxene microliths in process of development 

 (sp. gr. 2-46). 



Vungalei itself is only elevated about- 130 feet above the sea. 

 In proceeding from this village to Tembe, lying about two miles 

 S.S.W., one crosses a line of hills, about 600 feet in height, which 

 form a spur of the main range. Basic agglomerates similar to 

 those found on the slopes of Mount Vungalei, as described below, 

 prevail in the district between these two villages up to the top of 

 the intervening hills. In places one notices that they overlie the 

 ordinary sedimentary deposit, known as " soapstone," a slightly 

 calcareous clay-tuff but showing no organic remains to the eye. 

 The rock exposed in the stream-courses is a semi-ophitic basaltic 

 andesite (sp. gr. 274) which contains a considerable amount of 

 interstitial glass. 1 When proceeding S.S.W. from Tembe on the 

 way to Nandongo one passes on either hand, as described on 

 page 216, hills about 700 feet high displaying vertical cliffs formed 

 of agglomerates over-lying finer sedimentary beds apparently of 

 the " soapstone " character. 



I made the ascent of Mount Vungalei from the village of that 

 name. The peak is also known as Ndrukau. Basic agglomerates 

 were exposed all the way up to an elevation of about 2,000 feet, 

 where a bed of a somewhat scoriaceous basaltic andesite was dis- 

 played, the upper 200 feet being inaccessible but of the same 

 agglomerate. At a height of 300 feet was observed another layer 

 of the same basaltic rock. These intercalated beds appeared to 

 be lava-flows rather than horizontal dykes. The agglomerates 

 become less coarse in the upper part of the mountain where they 

 take the character of agglomerate-tuffs. The blocks are composed, 

 like those in many other parts of the island, of a dark semi- 

 vitreous basaltic andesite, but often scoriaceous. But the most 

 remarkable features of these agglomerates are the indications of 

 two distinct pauses in their deposition afforded by the occurrence 

 at elevations of 900 and 1,700 feet of a single horizontal bed, two 

 to three feet thick, of coarse palagonite-tuffs. Each bed is exposed 

 at the foot of a tall cliff of agglomerate forming a line of escarp- 

 ment along the mountain-side. The larger fragments making up 

 these tuffs are usually from 2 to 3 millimetres in size ; but 

 the process of palagonitisation is not complete ; and we find 

 inclosed abundant angular pieces of a dark fresh tachylyte-glass, 

 finely vesicular, and fusing readily in the ordinary spirit-lamp 

 flame. The tuffs contain little or no lime and seemingly no 

 1 Referred to genus 9 of the augite-andesites. 



